1. Field of the Invention
The invention relates to a voltage control of a digital circuit, and more particularly, to an automatic voltage control circuit and related method for dynamically adjusting a supply voltage according to the condition of the circuit operation.
2. Description of the Prior Art
In digital circuit design, one or more clocks are utilized to manage the synchronization of flip-flops such as D-type flip-flops (DFFs). When a clock triggers the flip-flop, the value at the data input node must be stable so that the flip-flop can sample the value correctly. Therefore, the clock frequency used by the digital circuit is limited by the signal transmission speed between the flip-flops. In other words, when designing the digital circuit, it is necessary to guarantee that the period of the clock is not less than the time required for signal transmission between flip-flops.
In digital circuits, however, many factors such as process, ambient temperature and supply voltage influence the signal transmission speed. The signal transmission speed may also become slower due to process variation, and increases in ambient temperature and decreases in supply voltage also result in slower signal transmission speeds. To confirm the circuit can correctly operate under varying conditions, a circuit design method called worst case analysis is introduced in the circuit design. But designing a circuit with this prior art method results in larger circuit layout area and greater power consumption during operation.
Power consumption is very important for electronic products, especially for portable electronic devices whose power is provided mainly by the batteries. Excess power consumption in the portable electronic device will rapidly exhaust the limited battery power and will shorten the standby/operating time. As a result, users are inconvenienced to change or recharge the batteries more often. Therefore, designers of electronic products constantly seek to decrease power consumption in their designs.